Filtering drinking water at the 'safe haven'. A safe haven was identified close to the campsite, with a clean water source, and an escape route in case of danger. The safe haven was also equipped with a communication line with the 'ground' team.

ESA’s cave training prepares astronauts to work as an international team in
real exploration conditions. Sending astronauts underground to survive and
explore Sardinian caves in Italy for almost a week is just one element of
their long training.

The Sardinian caves are isolated from the outside world. The astronauts need
to get used to confined spaces, minimal privacy, technical challenges and
limited equipment and supplies for hygiene and comfort - just like in space.